Enhancing the phytoremediation of petroleum-contaminated arid saline-alkali soil through irrigation-intercropping system combined with surfactants

In the Xinjiang oilfield exploitation area, the natural attenuation of petroleum hydrocarbons and plant growth is inhibited by the arid environment and saline-alkali soil conditions. By measuring the spatial distribution of salinity, alkalinity, and petroleum contamination in soil under drip irrigation (DRI), along with plant physiological indices, soil microbial abundance, and the remediation efficiency of plant intercropping systems, this study explored the impact of various concentrations of mixed surfactants on plant remediation capacity in two different local soil types under DRI. The results demonstrated that DRI facilitated the lateral migration of salt-alkali in the soil and increased plant growth at the DRI point. Compared to a ryegrass (Lolium perenne) monoculture, the combined biomass of cotton (Gossypium spp.) and ryegrass in a ryegrass-cotton intercropping system increased by 35.6% in loamy soil, and the phytoremediation efficiency of petroleum-contaminated soils in the intercropping system did not decrease. Periodic DRI with surfactants mitigated the downward migration of petroleum hydrocarbons, reducing the risk of underground pollution, and increased the abundance of petroleum-degrading bacteria as well as the efficiency of the intercropping system in remediating the soil. The intercropping system in loamy soil exhibited a more pronounced synergistic effect among the remediation elements than in sandy soil. This study demonstrated that the periodic application of surfactants and implementation of intercropping systems under DRI can effectively reduce petroleum pollutants in soil and can be considered a promising alternative for the phytoremediation of petroleum-contaminated saline-alkali soils in arid regions.